Bullae on the wrists of an 11―year-old boy

The findings of blood investigations (complete blood cell count and serologic tests for antinuclear antibody), urinalysis, and porphyrin studies were all unremarkable. Bullous lupus erythematosus was excluded by the paucity of clinical findings, a negative antinuclear antibody test result, and the histologie findings, while the normal results on plasma and urinary porphyrin screening made the diagnosis of erythropoietic porphyria unlikely.